具有布喇格反射层谐振器带内横模抑制结构设计

Design of in Band Transverse Mode Suppression Structure with Bragg Reflector Resonator

摘要:

研究了基于 X 切铌酸锂材料且具有布喇格反射层结构的谐振器，通过有限元（FEM）仿真模拟计算了面内旋转角和 Al电极厚度对机电耦合系数、相速度和阻抗比的影响。搭建三维有限元（3D FEM）结构探究了谐振器带内的横向模式与半周期的关系，并对比了两种小锤结构对横向模式的抑制作用，小锤结构无法对 SMR 谐振器的横向模式进行有效抑制。设计了 3 种加权谐振器结构，分别是加权无假指、加权有假指和加权有小锤。实验对比了普通谐振器与 3 种加权谐振器的性能。结果表明，3 种加权谐振器的机电耦合系数（K² ）都超过了 15%，阻抗比约为 60 dB，均对带内横向模式有明显的抑制作用。

Abstract:

Based on X-cut lithium niobate resonator with Bragg reflector structure （SMR）， the effects of in-plane rotation angle and Al electrode thickness on electromechanical coupling coefficient（K² ）， phase velocity， and impedance ratio were simulated and calculated via finite element （FEM） simulation. We constructed a three-dimensional finite element （3D FEM） structure to investigate the relationship between transverse modes and half wavelength within the resonator band and compared the suppression effect of transverse modes between two types of piston structures. However， the effect was not significant. Then three weighted resonator structures were proposed， namely weighted without dummy fingers， weighted with dummy fingers， and weighted with hammers. Subsequently， the performance of ordinary resonators was compared with three types of weighted resonators via experiments. The results show that the electromechanical coupling coefficient of the three weighted resonators exceeds 15%， and the impedance ratio is approximately 60 dB， which has a significant inhibitory effect on the transverse modes within the band.